Blender Git Loki

GP: Fix T56802 - Add/Delete Vertex Group crashes

Cloth: Improve UI

This reorganizes the cloth UI, and changes some of the behaviour to be
more reasonable.

Changes included here:
* Reorganized cloth panels
* Improved some tooltips
* Removed `vel_damping` option
* Removed cloth pinning checkbox
* Removed stiffness scaling checkbox
* Separated shrinking from sewing
* Separated self collisions from object collisions

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D3691

GPU module: Initial implementation of the `gpu.shader` submodule.

Differential Revision: https://developer.blender.org/D3688

Depsgraph: Use default visibility of false

Avoids invisible objects from being considered visible when they
are used as driver variables.

If those cases are actually coming from a visible object, then
deg_graph_build_flush_visibility() will ensure visibility is
properly flushed there.

Depsgraph: Respect parent object visibility in more places

Mainly coverts object->parent and pose constraints.

Depsgraph: Make indirectly linked objects inherit visibility from parent

This way objects which are pulled into dependency graph via modifier
stack from an invisible object will be invisible.

Depsgraph: Use explicit argument values

Multires: Initial work to get sculpting to work with OpenSubdiv

Allows to go to sculpt mode, do brush strokes, get out of sculpt mode
and have deformation preserved.

The issues currently is that the current implementation of CCG
storage is created from the limit surface, without displacement
taken into account. It is trivial to get displaced coordinates,
but it is more tricky to get displaced normals. This is something
to be solved next.

Another limitation is that this only works for sculpting at a maximal
multires level. There is code to be done to support propagation
of displacement onto a higher levels.

Subdiv: Cleanup, variable name spelling

Sculpting: Fix wrong object was using for PBVH

The function is supposed to be called for original object.
Draw manager abuses this a bit, will solve later by moving
PBVH (re)creation to dependency graph.

At the time being, stop adding object evaluation to draw
manager, this is really where it does not belong to.

Subdiv: Cache Subdiv in CCG surface

Allows to do re-shaping easier, since we will know for sure
what was the limit surface the CCG is created for.

GPUBuffers: Rework support for pbvh grids + fast navigate

Flat shaded grids are now rendered as a long triangle strip with
degenerate triangles.

Smooth shaded grids are not changed.

Also add back fast navigate. The only difference with 2.79 is that fast
navigate + flat shading will show slitly "incorrect" smooth face. But that's too
much effort to fix for what it is.

GP: Add thickness and stregth factor to UI

Now it's possible change the factors for soft eraser.

GP: Fix armature deformation weight problem

The armature was using only weight 1 or 0, but not the real value.

Also removed unused parm in UI panel.

GP: Change fill option text

GP: Add strength factor for eraser brush

This gives more control.

GP: More tweaks in soft eraser

Follow with the changes to get a good feeling using the eraser.

GP: Add pressure button for eraser brushes

Merge branch 'master' into blender2.8

Fix building deps when OpenCV dev package is present.

Since we are not linking against OpenCV ourselves, that generated
linking errors later on (while building OSL e.g.).
Those 'open' libs link against way too many other libs... :/

Thanks to @intrah for initial report (T56785), and @LazyDodo for
suggested solution.